<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>while 循环</title>
</head>

<body>
    <p>点击下面的按钮，只要 i 小于 5 就一直循环代码块。</p>
    <button onclick="myFunction()">点击这里</button>
    <p id="demo"></p>
    <script>
        function myFunction() {
            var x = "", i = 0;
            while (i < 5) {
                x = x + "该数字为 " + i + "<br>";
                i++;
            }
            document.getElementById("demo").innerHTML = x;
        }
    </script>
</body>

</html>